Electrical stringed instrument



June 13, 1967 y, Q CQOKERLY ET AL 3,325,579

ELECTRICAL STRINGED INSTRUMENT Filed March 30, 1965 I2 I3 I4 5 INVENTORSso l JACK c. cooKERLY Fle. BY GEORGE R. HALL ATTORNE S United StatesPatent O 3,325,579 ELECTRICAL STRINGED INSTRUMENT .laclr C. Cookerly,7566 Atoll Ave., North Hollywood, Calif. 91695, and George R. Hall,13613 Huston St.,

Sherman (laks, Calif. 91403 Filed Mar. 30, 1965, Ser. No. 443,958 7Claims. (Cl. 84-1.16)

ABSTRACT OF THE DISCLOSURE This disclosure relates to an improvedelectrical guitar wherein a uniquely designed magnet is employed toprovide a magnetic iield cutting across the strings over a portion ofthe length of the strings 4between the guitar nut and bridge. Themagnetic field configuration is such that the resulting current inducedin the strings as a consequence of vibration will have frequencies andamplitudes proportional to the frequencies and amplitudes of thevibrations themselves and may be passed through suitable wave-shapingcircuits and amplifier means to loud speakers. The magnetic fieldgenerating arrangement extends a suflicient distance along the length ofthe strings to result in a long sustaining output signal. In addition,the' electrical circuitry involved together with other features providesfor proper dampening of undesired resonances in the neck structure ofthe guitar. In this respect, the guitar neck includes a laminatedconducting plate which serves to dampen resonances in the neck and alsoserves to provide a current path for current induced in the strings.

This application is a continuation in part of our copending applicationSerial No. 244,376, now Patent No. 3,297,813, tiled ec. 13, 1962 andentitled, Electrical Instrument.

This invention relates generally to electrical instruments and moreparticularly to stringed instruments in which an electrical signal isgenerated in response to string vibrations for reproduction through aloud speaker.

An example of the type of electrical instrument with which the presentinvention deals is the electric guitar and for purposes of illustratingcertain embodiments of the invention, its use in conjunction with anelectric guitar will be described.

Conventional electric guitars incorporate some type of transducer meansfor generating an electrical signal in response to vibration of thestrings. Basically, two types of transducers are possible: iirst, anelectrostatic transducer wherein a change in capacity, for example, canbe effected in response to physical string vibrations, and thisresulting change in capacity electrically detected to provide thedesired output signal. Second, electromagnetic means wherein one or morecoils with magnetic cores are employed in conjunction with a string offerrous material which varies the coil eld when vibrating in such amanner that the desired output signal is generated in the coil.

The electrostatic transducer system is necessarily a high impedancedevice and, therefore, introduces a serious shielding problem in orderto eliminate hum. In addition, there is usually required a high D-Cpolarizing voltage which also necessitates shielding for practicalpurposes.

The electromagnetic type of pickup employing a coil ICC overcomes theobjection of high impedance, but it is very diicult to design in such amanner as to eliminate pickup from adjacent strings on the instrument.This latter problem can become very serious in electrical instruments ofthe type such as described in our co-pending patent application Ser. No.153,467, tiled Nov. 20, 1961, for Tone Generation System, wherein theoutput from each individual string is fed into a trigger circuit toprovide signals of double or half frequencies or of particular waveshapes. Such trigger circuits are sensitive and if there is not properisolation between the various strings, one may serve to trigger thecircuit associated with an adjacent string.

Moreover, in coil pickup type instruments, the strings of the instrumentmust include a ferrous material which restricts the player to the use ofpredominently iron strings as opposed to phosphor-bronze,beryllium-copper, or metallic coated nylon or gut type strings.

In addition to the above, in many present day transducer systems, thetransduced signal is different when the string is plucked towards ratherthan away from the pickup. This lack of symmetry diminishes the fidelityof the system.

Other problems relateto undesirable resonances generated in the bodyportion of the instrument upon which the strings are mounted. Withpresently available transducing systems, such undesirable resonantconditions are detected along with the desired string movements from theartists playing of the strings. It would be highly advantageous toincorporate in a transducer system means for minimizing or eliminatingsuch undesirable resonant conditions. i To avoid general bulkiness,present day transducer systems of -both the electrostatic andelectromagnetic type are miniaturized as much as posible. As aconsequence, only a very small portion of the string is employed toprovide the ,movement to be transduced. As a result, traveling harmonicsin the string tend to be accentuated. Stated differently, when only asmall portion of the string is employed, any traveling harmonicconstitutes a relatively large percentage of the string movement that istrans. duced. Further, the sustaining power of the string in present davtransducer systems is somewhat limited. Thus, even lthough the stringmay still vbe vibrating, the sound appears to drop off relativelyquickly rather than be sustained as is the case when the instrument isemployed as aconventional sound instrument.

With all of the foregoing in mind, it is a primary object of the presentinvention to provide a greatly improved electrical instrumentincorporating novel transducer means in which the foregoing problems aresubstantially eliminated. t

MoreA particularly, it is an object to provide in an electricalinstrument a low impedance transducer means to the end that shieldingmay be substantially eliminated.

Another Object is to provide a low impedance transducer for a stringedinstrument in which pickup from adjacent strings is substantiallyeliminated.

Another object is to provide a transducer for a stringed instrument inwhich the strings are not restricted to a ferrous material.

Another important object of this invention is to provide a transducerwhich may be polarized to the extent that undesirable resonancesresulting Ifrom vibrations in the strings in .given planes areautomatically eliminated.

Another object is to provide an improved transducer for a stringedinstrument which is compact, simple in construction, and avoids anybulky structure which might otherwise interfere with an artists attackon the strings.

Still another object is to provide a transducer in which the percentagecontent of traveling harmonics is greatly reduced and which has arelatively long sustaining power as compared to transducers presentlyavailable.

Another important object of this invention is to provide a noveltransducer means in combination with a neck structure and stringanchoring means in which undesirable resonances `are substantially`damped or broadened in such a manner as to result in an improved outputtone.

Briefly, these and many other objects and advantages of this inventionare attained by utilizing the strings of the instrument themselves 'aspart of the electrical pickup means. More particularly, the instrumentis provided with a magnetic field passing in a given direction acrossthe strings in such a manner that vibration of the strings in the fieldinduces currents in the strings themselves. The current in each stringis individually passed through an associated wave shaping and amplifiercircuit to an audio output.

`Since only a string that is moved will have a current induced therein,there is substantially no interference from adjacent strings so thatexcellent isolation between the individual strings is realized. Inaddition, by providing the magnetic field in a -given direction, onlymovement of the strings in planes cutting across or forming an anglewith this direction will result in the inducing of current in thestrings so that vibrations in undesirable planes as might result fromresonances, for example, will have substantially no effect on the outputsignal.

In the preferred embodiment of the invention, the magnetic field isestablished by a single elongated rectangularly shaped permanent magnet`cooperating with an L- shaped channel member. The arrangement is suchthat the top surface of the magnet constitutes one pole of the magneticfield and the top edge portion of the vertical part of the L-shapedchannel constitutes the other pole.

The structure is positioned beneath the strings close to the point atwhich the neck intercepts the body portion of the instrument andpreferably includes elongated strip members of magnetic material whicheffectively extend the inuence of the magnetic field to cover asubstantial length portion of the strings. As a consequence, thefundamental signal induced at any one instance is large compared to anytraveling harmonics along the string. Further, a desired sustainingpower is realized.

These foregoing lfeatures in combination with further mechanicalfeatures in the structure of the instrument for damping undesirableresonances results in a greatly improved electrical stringed instrument.

A better understanding of the invention will be had by now referring toa preferred embodiment thereof -as illustrated in the accompanyingdrawings, in which:

lFIGURE 1 is a perspective view, partly schematic in form and partlybroken away, illustrating the basic features of the electrical stringedinstrument of this invention;

FIGURE 2 is a fragmentary cross-section taken in the direction of thearrows 2--2 of FIGURE 1;

FIGURE 3 is a broken away enlarged perspective view of a portion of themagnetic field generating means incorporated in the instrument of FIGUREl; and

FIGURE 4 is a `cross-section taken generally in the direction of thearrows 4-4 of FIGURE 1 useful in eX- plainin-g certain features of theinvention.

Referring first to FIGURE 1, there is shown a stringed instrument in theform of a guitar designed in accordance with the present invention. Theguitar includes a body having an elongated neck portion 11. The guitarstrings are illustrated at 12, 13, 14, 15, 16, and 17 and have firstends passing over the conventional nut 18 and secured to suitable tuningpegs 19. A shunting bar `20 of electrically conducting material isbridged across the strings beyond the nut and serves to electricallyconnect the first ends of all of the ystrings together.

The peg board portion of the neck also includes an enlargement indicated4at 21, the purpose for which will be described in ygreater detail asthe description proceeds.

Still referring to FIGURE 1, the second ends of the strings pass over asuitable bridge designated generally by the numeral 22 and are anchoredas by pegs 23 to the gui-tar body. The bridge structure 22 and anchoringmeans 23 .are preferably as described and claimed in our copendingpatent application Ser. No. 308,870, filed Sept. 13, 1963 and entitledStringed Instrument Bridge and Anchoring Means.

A-t the anchoring means 23, the strings are respectively connected to acorresponding number of conductors passing from the body 10 as indicatedat 24. These conductors, in turn, respectively connect to individualwave shaping and amplifier circuits `designated generately at 25. T-heindividual outputs from each of these circuits, in turn, are passed to asuitable speaker system 26.

With particular reference now to FIGURE 2, it will be noted that thefirst ends of the strings which are shunted by the shunting bar 20electrically connect to an elongated conducting strip 27, preferablyaluminum, and incorporated in the neck of the guitar as part of alaminated structure. The speed of sound in the strip 27 is differentfrom the speed of sound in the surrounding material-s of the laminationand as a consequence, the resonance curve for the neck is damped.Further, the resonant curve is broadened by the provision of theenlargement 21 described in FIGURE 1 and as shown in FIG- URE 2.

The feature of la laminated neck and the manner in which the enlargementeffects a desired broadening of the resonance curve to shift the nodalpoint to correspond to the area of the nut with resultant improvement inthe guitar construction lis fully set forth in our copending applicationSer. No. 308,871, vfiled Sept. 13, 1963 and entitled, Guitar NeckConstruction. In view of the elimination of spurious -signals resultingfrom resonance and the like in the instrument body itself, thecombination of the neck structure shown in FIGURE 2 with the novelelectrical transducer means of the present invention constitutes animportant overall combination, as each feature contributes to the otherin providing an improved electrical signal output.

With respect to the foregoing, the strip 27 serves as a conductingmedium for grounding the shunting bar 20 at a point 28 so that all ofthe wires for the instrument may be brought out at a desired singlepoint in the body and it is not necessary to run a special wire up tothe shunting bar 20. The str-ip 27 thus serves the dual function ofproviding a desired damping of the resonance in the neck as well as aconductor for the shunting bar 20.

Referring now to FIGURE 3, the actual means for generating a magneticfield to induce currents in the various strings 12-17 is shown. Thismagnetic field generating means comprises an elongated generallyrectangularly shaped magnet 29 cooperating with an L-shaped channelmember 30. The magnet is disposed along an edge portion of thehorizontal part of the L-shaped channel as at 31. The magnet 29 has itstop surface of one polarity and its bottom surface of the oppositepolarity as indicated by the letters N and S. The L-shaped channelmember 30 is of magnetic material and serves to eX- tend the south poleover to the left as viewed in FIG- URE 3 and up to the top edge of thevertical part 32 of the channel.

In addition tothe magnet and L-:shaped channel, there are providedelongated strips 33 and 34 which respectively overlie the top surface ofthe magnet 29 and the upper edge of the vertical part 32 as shown. Theorientation of the strips can be seen in the broken away portion ofFIGURE 1. These strips are of magnetic material and extend beyond thefar ends of the magnet and L-shaped channel structure to effectivelyfunction as pole pieces and extend the infiuence of the magnet fieldpassing between the top surface at the magnet 29 and vertical part 32 ofthe channel 30. By this arrangement., a substantial portion of thelength yof the strings are within the magnetic field and thus the signalinduced in each of the strings in cutting the magnetic field ispredominently due to the fundamental motion of the string, the harmonicshaving considerably less effect as a result of the length of stringWithin the field.

FIGURE 4 illustrates schematically by the arrow 35 the Idirection of themagnetic field as generally parallel to the plane of the strings 12-17.However, when the strings are plucked or played, their directioinalmotion is generally in the direction of the double headed arrow 36 whichis substantially at right angles to the magnetic field so that -amaximum signal is induced in the strings.

In the overall operation of the electrical stringed instrument of thisinvention, wherever one or .more strings are played, the resultingvibration will cause the string to cut the magnetic field as illustratedin FIGURE 4.. As a consequence, there will be a current induced directlyin the moving string, which current will be conducted by the stringitself through one of the leads 24 to the correspondingly connected Waveshaping and amplifying circuit. By way of specific example, each of thewave shaping and amplifier circuits 26 may be of the type shown anddescribed in our co-pending application Ser. No. 153,467, filed Nov. 20,1961, and entitled, Tone Generation System. In this prior application,the transducing means employed is different from the instant transducingmeans in that the signal is induced in a coil as a consequence of themoving string. However, the output signal from the string itself as isthe case in the present invention co-uld be fed into :amplifier and waveshaping circuits such as shown and described in said co-pendingapplication.

In addition, the wave shaping and amplifier circuits may includesuitable tone level control circuits such as shown and described in ourco-pending `application Ser. No. 198,642, filed May 29, 1962 andentitled, Tone Level Control Circuit.

The electrical signal induced and carried by each of the strings resultsin an eventual out-put which is far superior than is afffforded byconventional pickup means such yas the capacitive or inductive typesdescribed heretofore.

Furthermore, the only restriction on the strings is that they beconductive so that strings of the phosphorbronze or beryllium coppertype, or metallic wrapped nylon 0r gut found on classical acousticguitars may be used. This latter feature is important lin that theelimination of ferrous strings heretofore thought necessary in electricguitars also eliminates various -undesirable characteristics of ferrousstrings; for example, lack of good vibrating character-ictics at thehigher tones, high tension `required in the strings, and discomfort to aplayers fingers.

From the foregoing description it will thus `be evident that the presentinvention has provided a greatly improved electrical stringedinstrument. Not only are the Various advantages and objects of thisinvention as set forth heretofore fully realized rby the novelelectrical pickup means in which the strings themselves are employed aspart of the conducting circuit, but this feature in combination with theimproved bridge and anchoring means and laminated neck construction andWeight means as described in the various referred to co-pendingapplications results in an electrical instrument vastly superior to anythat has been available heretofore.

What is claimed is:

1. In a musical instrument including a body and a plurality of stringsstretched across a portion of said body, means for providing a magneticfield in a given direction transverse to said strings; and electricalmeans connected to said strings for converting current induced in saidstrings as a consequence of vi-brational movement in said magnetic fieldinto electrical signals of magnitudes and frequencies constitutingfunctions of the magnitudes and frequencies of vibration of saidstrings, said means for providing a magnetic field comprising anelongated rectangularly shaped magnet having its top surfacel of onepolarity and its bottom surface of an opposite polarity; an L-shapedchannel member of magnetic material, said magnet being positioned alongthe free edge portion of the horizontal part of said L-shaped channel,the vertical part of said channel defining a pole corresponding to thepolarity of the bottom surface of said magnet so that the givendirection of said field is from the top surface of said magnet to theupper edge of the vertical part of said L-shaped channel; and elongatedstrips of magnetic material overlying said magnet and top edge of saidL-shaped channel, respectively, in positions on either side of saidstrings to extend the lengths of said strings intercepting said magneticfield.

2. An electrical instrument comprising, in combination: a body having aneck portion extending from one end thereof and terminating in tuningstops; a plurality of strings stretched over said body and secured tosaid tuning stops; a nut adjacent to said tuning stops over whichportions of said strings pass; a bridge secured to said body; saidstrings passing over said bridge and being secured to said body atpoints adjacent to said bridge; means for providing a magnetic field ina given direction disposed adjacent to said strings between said nut andbridge; means electrically connecting first ends of said strings toground; and a plurality of individual wave shaping circuits and`amplifier means connected respectively to second ends -of said strings,each of said strings including electrically conducting material so thatmovements of said strings in planes at an angle to said given directionto cut said magnetic field generates electrical currents in saidstrings, said currents being modified and ampified by said Wave shapingcircuits and ampifier means, respectively, to provide electrical signalsconstituting functions of the frequencies and amplitudes of saidmovements of said strings.

3. An instrument according to claim 2, in which said given `direction isoriented in a position substantially parallel to the direction ofmovement of said strings resulting from resonant conditions in said bodyand neck and substantially at right angles to the direction of movementof said strings resulting from playing of said strings, whereby currentsresponsive to movement of said strings resulting from resonantconditions in said body and neck are substantially reduced.

4. An instrument according to claim 2, in which said neck portionincludes an enlargement adjacent said tuning stops to broaden theresonant curve of said neck portion the same as though said neck portionextended an increased distance beyond said nut.

5. An instrument according to claim 2, in which said means forgenerating a magnetic field includes an elongated rectangular shapedmagnet having a top surface of one polarity and a bottom surface of anopposite polarity; an L-shaped channel member of magnetic material, saidmagnet being positioned along the free edge portion of the horizontalpart of said L-shaped channel, the vertical part of said channeldefining a pole corresponding to the polarity of the bottom surface ofsaid magnet so that said given direction of said field is from the topsurface of said magnet to the upper edge of the vertical part of saidL-shaped channel; and elongated strips of magnetic material overlyingsaid magnet and top edge of said L- shaped channel, respectively, saidmagnet and L-shaped channel being positioned beneath said strings withsaid strips extending adjacent to either side of said strings lalong asubstantial length of said strings.

6. An instrument according to claim 2, in which said neck is of alaminated construction, one of the laminations constituting a metallicstrip, said means connecting said ends of said strings to groundincluding, in part, said metallic strip, said metallic strip serving theadditional function of dampening resonant conditions in said neckportion as a consequence of the difference in acoustic speed of sound insaid strip as compared to the acoustic speed of soun-d in the remainingportion of said neck.

7. An instrument according to claim 2, in which said plurality ofstrings include a non-ferrous electrically conducting material.

References Cited UNITED STATES PATENTS ARTHUR GAUSS, Primary Examiner.

B. P. DAVIS, Assistant Examiner.

1. IN A MUSICAL INSTRUMENT INCLUDING A BODY AND A PLURALITY OF STRINGSSTRETCHED ACROSS A PORTION OF SAID BODY, MEANS FOR PROVIDING A MAGNETICFIELD IN A GIVEN DIRECTION TRANSVERSE TO SAID STRINGS; AND ELECTRICALMEANS CONNECTED TO SAID STRINGS FOR CONVERTING CURRENT INDUCED IN SAIDSTRINGS AS A CONSEQUENCE OF VIBRATIONAL MOVEMENT IN SAID MAGNETIC FIELDINTO ELECTRICAL SIGNALS OF MAGNITUDES AND FREQUENCIES CONSITUTINGFUNCTIONS OF THE MAGNITUDES AND FREQUENCIES OF VIBRATION OF SAIDSTRINGS, SAID MEANS FOR PROVIDING A MAGNETIC FIELD COMPRISING ANELONGATED RECTANGULARLY SHAPED MAGNET HAVING ITS TOP SURFACE OF ONEPOLARITY AND ITS BOTTOM SURFACE OF AN OPPOSITE POLARITY; AN L-SHAPEDCHANNEL MEMBER OF MAGNETIC MATERIAL, SAID MAGNET BEING POSITIONED ALONGTHE FREE EDGE PORTION OF THE HORIZONTAL PART OF SAID L-SHAPED CHANNEL,THE VERTICAL PART OF SAID CHANNEL DEFINING A POLE CORRESPONDING TO THEPOLARITY OF THE BOTTOM SURFACE OF SAID MAGNET SO THAT THE GIVENDIRECTION OF SAID FIELD IS FROM THE TOP SURFACE OF SAID MAGNET TO THEUPPER EDGE OF THE VERTICAL PART OF SAID L-SHAPED CHANNEL; AND ELONGATEDSTRIPS OF MAGNETIC MATERIAL OVERLYING SAID MAGNET AND TOP EDGE OF SAIDL-SHAPED CHANNEL, RESPECTIVELY, IN POSITIONS ON EITHER SIDE OF SAIDSTRINGS TO EXTEND THE LENGTHS OF SAID STRINGS INTERCEPTING SAID MAGNETICFIELD.